The present invention relates to a gas-tight seal for a gas supply system of metal, in particular for sealing an airbag gas supply system, and to a method of manufacturing a gas-tight seal.
Airbag systems are increasingly used in motor vehicles. They have come to be used at different positions in the vehicle in order to absorb lateral as well as frontal collisions. These airbag systems are partially equipped with gas conducting conduits of metal. The dimensions and the material of the walls of these conduits are such that the gas supply system is sufficiently gas tight so as to withstand the high pressures occurring when the airbag is triggered. The ends of the conduits are fixed to the vehicle if necessary in order to securely fasten the airbag system.
The gas-tight seal of these gas supply systems must have an endurance of 5 seconds in accidents involving roll-overs of the vehicle. After this, the pressure is reduced in order to release the passengers out of the vehicle. Hitherto, in some approaches the seal has been a plastic stopper which was inserted into the open end of the gas supply system and which then had to be connected, usually crimped, to the conduit in a gas-tight manner. This approach involved a lot of material because, in order to achieve sufficient gas tightness, the stopper had to reach sufficiently deep into the gas supply system and the tightness of the connection required elaborate fastening.
According to DE 100 22 462 it is suggested that an end cap, which is of the same material as the conduit itself, be welded onto the end of the conduit, preferably using laser welding, electron welding or arc welding techniques. These welding techniques are expensive and require high precision.
JP 57064427 A describes the insertion of an elastic layer of aluminium, copper and rubber into the end of a tube and the subsequent compression of the tube end under controlled pressure. The compression is carried out against a template in order to ensure correct forming. After closing the tube end, the template must be removed from the free end of the tube, and if necessary a further coupling piece of the tube is joined. The process is complex and, with the use of the template, is economically feasible only in a few cases.